HEM SHEELA MODEL SCHOOL DURGAPUR

HEM SHEELA MODEL SCHOOL DURGAPUR CLASS 12 PHYSICAL EDUCATION REVISION NOTES BY SOURABH LAHIRI & ANJAN KR BISWAS K ey Poi n ts: Pr ojectile & factor s affecting pr ojectile tr ajector y New ton's law s of m otion and their application in spor ts Aer odynam ics pr inciples Fr iction & Spor ts I ntr oducation to Ax es And Plane T ypes of m ovem ents( Flex ion, E x tension, Abduction, Adduction) M ajor m uscle involved in R unning, Jum ping And T hr ow ing Pr ojecti l e Pr ojectile: an object thr ow n into the space either hor izontally or at acute angle under the action of gr avity is called a pr ojectile. I n the field of gam es and spor t ther e ar e m any ex am ples of pr ojectiles such as putting the shot, thr ow ing a ham m er, discus and javelin in athletics. F a ctor s a f f ecti n g pr ojecti l e tr a jector y Pr opelling For ce : T he pr opelling for ce pr oduces cer tain effects depending upon its point and dir ection of application. I f the application is dir ectly thr ough the pr ojectile's centr e of gr avity, only linear m otion r esults fr om the for ce. As the pr ojecting for ce is m oved fur ther fr om the centr e of gr avity, r otator m otion of the object incr eases at the ex pense of linear m otion. I f the for ce is below the object's centr e of gr avity, back spin is r esults. For w ar d spin r esults w hen the for ce is above the centr e of gr avity. W hen the for ce is off centr e to the left, clock w ise spin r esults and w hen it is off centr e to r ight, counter clock w ise spin occur s. For ce of Gr avity: As soon as contact is br ok en w ith a pr ojected object, the for ce of gr avity begins to dim inish the upw ar d velocity of the object. Finally, gr avity over com es the

effects of the upw ar d com ponent of the pr ojectile's m otion and the object begins to descend. T he factor s that deter m ine how soon gr avity w ill cause the object to descend ar e - (a) W eight (m ass) of the object (b) am ount of for ce dr iving it upw ar d (C) the effect of air r esistance on the object. (iii) E ffect of Air R esistance As the speed of an object incr eases, air r esistance has a gr eater r etar ding effect. T he m or e sur face ar ea an object pr esents in the dir ection ofm ovem ent, the gr eater w ill be the effect of air r esistance. Pr ojecti l e & f a ctor s a f f ecti n g P r ojecti l e T r a jector y Speed of R elease Angle of R elease(t r ajector y of R elax ) H eight of R elease N ew ton s l a w s of m oti on a n d th ei r a ppl i ca ti on i n th e f i el d of spor ts. T he thr ee law s of m otion for m ulated by New ton ar e descr ibed below 1.L aw of iner tia: Accor ding to this law a body at r est w ill r em ain at r est and a body in m otion w ill r em ain in m otion at the sam e speed and in the sam e dir ection unless acted upon by an ex ter nal for ce. T her e ar e gr eat ex am ples of this law in spor ts such as star ting in r ow ing, star ting in spr inting, star ting in thr ow ing the ham m er. B asically if an object is in m otion, it r em ains in m otion unless som ething or som e ex ter nal for ce stops it. T he ex ter nal for ce m ay be gr avitational for ce, the sur face of playing field or a defensive player etc.for E x : Star ting in spr inting, star ting in r ow ing, star ting in ham m er thr ow. 2.L aw of acceler ation: Accor ding to this law, A change in m otion is dir ectly pr opor tional to the for ce pr oducing it and inver sely pr opor tional to its m ass. I f tw o unequal for ces ar e 2 / 6

applied to objects of equal m ass, the object that has gr eater for ce applied w ill m ove faster. Conver sely, if tw o equal for ces ar e applied to objects of differ ent m asses, the lighter m ass w ill tr avel at a faster speed.eg. in ham m er thr ow, a thr ow er w ho is str onger w ill thr ow the ham m er far ther than a thr ow er w ho is less str onger. 3.L aw of r eaction: Accor ding to this law For ever y action ther e is an equal and opposite r eaction. T her e ar e so m any ex am ples in spor ts w her e this law is applied. e.g., I n sw im m ing a sw im m er pushes the w ater back w ar ds (action) and the w ater pushes the sw im m er for w ar d (r eaction) w ith the sam e for ce. I n sw im m ing, a sw im m er pushes the w ater back w ar ds(action). T he w ater pushes the sw im m er for w ar d( r eaction) w ith the sam e for ce. A er ody n a m i cs is the study of pr oper ties of m oving air and the inter action betw een the air and solid bodies m oving betw een it. T h e ba si c f or ces of a er ody n a m i cs ar e stated below : L i f t: lift is the for ce that pushes the object to m ove upw ar d. I t is the for ce that is the opposite of w eight. W ei gh t: W eight is the for ce gener ated by the gr avitational for ce of the ear th. T he w eight of an object contr ols how str ong the push has to be. A shot of 16 pounds r equir es m or e for ce (push) than a javelin. Dr a g: Dr ag is a for ce that tr ies to slow the object dow n. I t m ak es har d for an object to m ove. I t is har der to w alk thr ough the w ater than thr ough the air. I t is because w ater causes m or e dr ag than air. T h r u st: T hr ust is a for ce that is the opposite of dr ag. T hr ust is the push that m oves som e objects for w ar d. F r i cti on a n d i ts ty pes T he for ce acting along tw o sur faces in contact w hich oppose\ the m otion of one body over the other is called the for ce of fr iction. I t is ver y im por tant in spor ts. T hat lagged the ar ea of contact betw een the sur faces, the gr eater is the for ce of fr iction. W hen both the sur faces ar e sm ooth, the for ce of fr iction r educes to alm ost zer o. T hr ee types of fr iction ar e (i) Static Fr iction T he opposing for ce that com es into plc w hen one body tends to m ove over the another sur face but the actual m otion has not yet r ed 3 / 6

(ii) L im iting Fr iction L im iting fr iction is the m ax im um of thing for ce that com es into play w hen one body is just on the ver ge of m oving over the sur face of another body. iii) K inetic Fr iction K inetic fr iction is the opposing for ce at com es into play w hen one body is actually m oving over the sur face of another body. A x es & P l a n e Plane is an im aginar y, flat sur face passing thr ough the body or gan or plane is the sur face on w hich the m ovem ent occur s. T her e ar e follow ing types of planes: a) Sagittal or M edial plane: T he sagittal plane is a ver tical plane passing fr om the r ear to the fr onty, dividing the body into left and r ight halves. I t is also k now n as anter oposter ior plane. M ost of the spor ts and ex er cise m ovem ents that ar e tw o dim ensional, such as r unning, long jum ping and som er sault tak e place in this plane. b) Fr ontal or Cor onal plane: the fr ontal plane is also ver tical and passes fr om left to r ight dividing the body into poster ior to anter ior halves. I t is also k now n as cor onal plane. Fr ontal plane cuts the body into fr ont and back.m vem ents along the fr ontal plane can include car tw heel and star jum ps. c) T r ansver se or H or izontal plane: T he tr ansver se plane divides the body into top and bottom halves. I n fact, it divides the body into upper and low er sections. T his plane lies hor izontally that w hy it is also called hor izontal plane. M ovem ents along this plane can include an icesk ating spin or r otation to play a tennis shot. A n a x i s is a str aight line ar ound w hich an object r otates. M ovem ents at the joints of hum an m uscosk eletal system ar e m ainly r otational and tak e place about a line per pendicular to the plane in w hich they occur. T his line is k now n as ax is of r otation. T her e ar e follow ing types of ax es of r otation: a) Sagittal ax is: T he sagittal ax is passes hor izontally fr om poster ior to anter ior. I t is for m ed by the inter section of the sagittal and tr ansver se plane. Sagittal ax is passes fr om fr ont to back. b) Fr ontal ax is: T he fr ontal ax is passes hor izontally fr om left to r ight. I t is for m ed by the 4 / 6

inter section of fr ontal and hor izontal plane. Fr ontal ax is passes fr om side to side. c) V er tical ax is: T he ver tical ax is passes ver tically fr om infer ior to super ior. I t passes str aight thr ough the top of the head dow n betw een feet. I t is for m ed by the inter section of sagittal and fr ontal plane. I t is also k now n as longitudinal ax is. I t is the longest ax is. T y pes of m ov em en ts T her e ar e var ious types of m ovem ent in body par ts w hich can be divided in four types i.e. gliding & angular m ovem ents, cir cum duction & r otation and few other m ovem ents. G l i di n g m ov em en ts: Gliding m ovem ents is the sim plest k ind of m ovem ent that can tak e place in a joint, one sur face gliding or m oving over another w ithout any angular or r otator m ovem ent. A n gu l a r m ov em en t: Angular m ovem ent occur s betw een long bones. B y angular m ovem ent the angle betw een the tw o bones incr eased or decr eased. T he var ious m ovem ents w hich fall under angular m ovem ents ar e descr ibed below : a) F l ex i on : B ending par ts at a joint so that the angle betw een them decr eases and par ts com e closer together (bending the low er lim b at the k nee). b) E x ten si on s: Str aightening par ts so that the angle betw een them incr eases and par ts m oves far ther apar t (str aightening the low er lim b at the k nee). c) A bdu cti on m eans m oving a par t aw ay fr om the m idline (lifting the upper lim b hor izontally to for m a r ight angle w ith the side of the body)) d) A ddu cti on m eans m oving a par t tow ar ds the m idline ( r etur ning the upper lim b fr om the hor izontal position to the side of the body). Ci r cu m du cti on : Cir cum duction is that m ovem ent w hich tak es place betw een the head of a bone and its ar ticular cavity. T his k ind of m otion is best seen in the shoulder and hip joints. R ota ti on : R otation is a for m of m ovem ent in w hich a bone m oves ar ound a centr al ax is w ithout under going any displacem ent fr om the ax is. M oving a par t ar ound an ax is is called r otation.eg. T w isting the head fr om side to side. M a jor m u scl es i n v ol v ed i n r u n n i n g T he m ajor m uscles involved in r unning ar e descr ibed below : 5 / 6

Glutes: these m uscles stabilize your hips and legs. T hese m uscles w or k w ith ham str ing m uscles and help in hip flex or s. Quads: Quads pr opel you for w ar d and help str aighten out the leg in fr ont so that it can m ak e a good contact w ith the sur face of gr ound. Calves: these m uscles give you spr ing in your step and at the sam e tim e these m uscles act as shock absor ber s. H am str ings: As you m ove for w ar d, the action sw itches to your ham str ings, the m uscles at the back of your thigh m uscles. T hese m uscles helps you in pulling the leg back behind and give you str ength to pr opel your body for w ar d. Cor e m uscles: Str ong abs and back ar e r eally im por tant because they k eep your s postur e upr ight and over all for m good. T hese m uscles play a significant r ole in r unning. B iceps: biceps also play a vital r ole in r unning. B iceps m aintain a bent ar m and help in sw inging your ar m s back and for th w hile r unning. M a jor m u scl es i n v ol v ed i n ju m pi n g & th r ow i n g T he leg, feet and gluteus m uscle gr oups ar e used in jum ping. Specific m uscles w hich ar e involved in jum ping ar e gluteus m ax im us, ham str ings, quadr iceps and soleus. I n fact, jum ping occur s in thr ee stages. T he fir st stage is the pr epar ator y stage w her e ank le m uscles calf m uscles and soleus tense to pr epar e launching. T he second phase is the launch phase, w her e hip ex tensor s, the ham str ings and gluteus m ax im us com bine and the k nee ex tensor s ex tend the k nees to allow the body to launch into the air. I n the last stage is the landing phase w her e all the m uscles em br ace im pact and allow the body to r etur n to a r esting position. T he m ajor m uscles ar e pector ials, m ajor, latissim us dor si, anter ior deltoid and ter es m ajor ar e involved in thr ow ing. T hese m uscles ar e com par atively r esponsible for velocity dur ing the thr ow. T he pector ials m ajor is the lar ge m uscle in the chest and latissim us dor si ar e the lar ge m uscles on each side of the back. Deltoid, biceps, tr iceps ar e also involved in thr ow ing a javelin in athletics. 6 / 6